KR20080047141A - Apparatus and method for generation a plasma - Google Patents

Abstract

An apparatus and a method for generating plasma are provided to process the plasma on an overall surface of a substrate by suppressing a local temperature from rising due to concentration of the plasma on one side. An apparatus for generating plasma includes a plurality of linear-type electrode bars(100), an upper power supply unit(102a), and a lower power supply unit(102b). The linear-type electrode bars are arranged at a predetermined interval. The upper power supply unit and the lower power supply unit are provided on the top and the bottom of each electrode bar so that any one electrode bar and a neighboring electrode receive power in reverse direction respectively. The electrode bar receiving power supplied from the upper power supply unit receives power having the phases of 0 and 180° alternatively. The electrode bar receiving the power supplied from the lower power supply unit receives the same power having a predetermined phase.

Description

Plasma generator and method {APPARATUS AND METHOD FOR GENERATION A PLASMA}

1 is a block diagram of a conventional apparatus for generating a plasma by using a ladder-shaped electrode array structure.

2 is a block diagram of a plasma generating apparatus according to a preferred embodiment of the present invention.

3 is a block diagram of a plasma generating apparatus according to another embodiment of the present invention.

4 is a flowchart of a thin film forming process using the plasma generating apparatus of the present invention.

5 is a thin film etching process flow chart using the plasma generating apparatus of the present invention.

* Description of the symbols for the main parts of the drawings *

102a: upper power supply unit 102b: lower power supply unit

103a: first matching portion 103b: second matching portion

104a, 104b: power distribution line 100: electrode

130: first standing wave 140: second standing wave

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film formation having improved plasma uniformity. In particular, the present invention relates to a plasma generator for improving the uniformity of a thin film by controlling a position of standing waves by supplying other power in addition to two powers having different phases. And to a method.

The high frequency plasma generator is used for the production of semiconductor films such as amorphous silicon, microcrystalline silicon, polycrystalline thin film silicon, silicon nitride, etc. used in solar cells, thin film transistors, and the like, and etching of semiconductor films.

Conventionally, when the film is formed using a high-density plasma, a 13.56 MHz radio frequency (RF), which is a practical power supply frequency, is used, but an ultrahigh frequency (VHF) of 27 MHz or more is used to improve the film formation speed, film characteristics, and etching speed. When the ultra-high frequency (VHF) of 27 MHz or more is smaller than 1/4 of the wavelength, the effect of the standing wave does not appear, and thus plasma may be uniformly deposited on the substrate. However, in the case of using a large-area substrate, for example, in the case of a substrate having a large area of 1 m * 1 m or more, standing waves are generated from the electrode, so that plasma is not formed uniformly. In other words, when the electrode is large, standing waves are generated on the surface thereof, and thus plasma is unevenly formed.

In order to solve this problem, a technique for generating plasma using a ladder-shaped electrode structure has been proposed.

FIG. 1 is a block diagram of an apparatus for forming a plasma using such a ladder-shaped electrode structure.

Referring to FIG. 1, a plurality of electrode rods 1 facing a predetermined substrate (not shown) are connected by a pair of connecting rods 2 and 2 ′ and provided with a ladder electrode 10 provided in a ladder shape. do. The ladder electrode 10 has the function of a discharge electrode. A power feeding circuit for supplying power to the electrode 1 is provided.

The power supply circuit includes a high frequency oscillator 21 for oscillating ultra high frequency, and a distributor 22 for distributing ultra high frequency oscillated by the high frequency oscillator 21. A pair of amplifiers 24, 24 'are provided such that the ultra-high frequencies distributed by the divider 22 are transmitted and amplified through different paths. Feeding lines 26 and 26 'are provided to supply the amplified ultra-high frequency to the electrode 1 through the matching portions 25 and 25', respectively. The feed lines 26 and 26 ′ are connected to connecting rods 2 and 2 ′ connecting the electrode rods 1. Two feed points (a, b) (c, d) are present in the connecting rods (2) and (2 '), respectively. In addition, a phase shifter 23 is provided in any one of the paths distributed to the distributor 22 to transmit the ultra high frequency. The phase shifter 23 performs phase modulation such that the ultra-high frequency distributed by the divider 22 has a phase different from that of other ultra-high frequencies. This is to improve non-uniform film formation characteristic due to standing waves generated by the ultra-high frequency.

In addition, although not shown in front of the amplifier (24) (24 ') to prevent the loss caused when the ultra-high frequency distributed by the divider 22 and applied through one path is supplied by flowing back to the other path An isolator is provided.

When two ultra-high frequency powers distributed by the distributor 22 are simultaneously supplied to the ladder electrode 10 having such a configuration, and the phase shifter 23 changes the phase difference of the ultra-high frequency with time, the 2 The standing waves formed by the two ultra-high frequencies may be changed in time to form a plasma having the same thickness on the entire surface of the substrate. In other words, the ladder electrode 10 structure can adjust the position of the standing wave according to the phase shift of the phase shifter 23 so that the density of the plasma can be uniformly processed.

However, the ladder electrode structure has the following problems.

In the plasma treatment process in which the ladder electrode structure is used, the position of the standing waves is adjusted by changing the phase, so that the plasma is not treated uniformly, but a uniform plasma treatment effect is obtained by scanning the non-uniform standing waves.

Therefore, the thin film formed at this time has a uniform power (Power) as a time average, but because of the characteristics that change over time, there is a problem that the plasma treatment effect is different depending on the time.

Accordingly, an object of the present invention is to provide a plasma generating apparatus and method for forming a thin film having excellent uniformity in film thickness by generating a uniform plasma even when time changes. have.

A feature of the present invention for achieving the above object is a plurality of straight electrodes arranged at regular intervals, and any one electrode and the neighboring electrode of the electrode is the top and bottom of the electrode to receive power in the opposite direction from each other The upper power supply unit and the lower power supply unit is provided in, the electrode that is powered by the upper power supply unit has a phase of 0 ° and 180 ° so that the power is alternately supplied to each other and the power is supplied by the lower power supply unit The supplied electrode is configured to supply the same phase.

A power distribution structure is formed in the upper and lower power supply units so that power is equally supplied to the electrode.

One power supply unit for supplying power to the electrode may be provided and configured to supply power to the top and bottom of the electrode by a switching means.

The electrode is one of a structure in which anodized aluminum, SUS, a material coated with an insulating material around a metal rod, and the like in a tube state, and the insulating material may be Si02, quartz, Teflon, or the like. In addition, the electrode may have a structure capable of introducing gas into the chamber in the plasma film forming and etching apparatus.

The electrode is characterized in that one end is floating (floating) or grounded.

The high frequency power source uses a very high frequency of several hundred MHz or more from a radio frequency of 13.56 MHz.

In addition, according to another feature of the invention, the step of heating the substrate provided in the chamber to a predetermined temperature, supplying the mixed gas through the discharge hole (or discharge rod installed in other parts) of the electrode rod of claim 1 inside the chamber In the step of supplying the mixed gas, two powers of different phases are sequentially applied from the upper part of the electrode by the upper power supply part while the other electrode positioned between the electrodes to which the power is applied is connected by the lower power supply part. Receiving a power having the same phase at the bottom of the electrode, Adjusting the phase difference of the two standing waves formed in the electrode structure is arranged the electrode due to the power supply, Uniformly formed in the electrode structure by the phase difference control Forming a thin film on the substrate by means of a plasma being formed.

In addition, according to another feature of the present invention, the step of supplying the etching gas through the discharge hole formed in the electrode into the chamber in which the thin film-formed substrate is installed, applying two electric power of different phase at the top of the electrode and applying the power The other electrodes located between the received electrodes are applied with power having an arbitrary phase from the bottom, adjusting the phase difference between two standing waves formed in the electrode structure in which the electrodes are arranged by the power supply, and adjusting the phase difference. And etching the thin film formed on the substrate by a plasma uniformly formed in the electrode structure.

It is preferable that the phase can be arbitrarily adjusted by the power supplied from the bottom of the electrode. The position of formation of the standing wave is changed by the phase adjustment.

Phases supplied to the upper part of the electrode are alternately supplied with phases of 0 ° and 180 °. At this time, when the phases are supplied separated by 180 °, the two standing waves have a phase difference of π / 2.

The plasma is uniformly formed by mutual interference between two electric powers supplied to the upper part of the electrode and one electric power supplied to the lower part of the electrode.

According to the present invention having such a configuration, even if the time is changed, the power having an arbitrary phase is supplied from the lower part of the electrode bar, it is possible to improve the uniformity of the plasma to form an excellent thin film.

Hereinafter, a plasma generating apparatus and a method according to the present invention will be described in detail with reference to a preferred embodiment shown in the accompanying drawings.

2 is a block diagram of a plasma generating apparatus according to a preferred embodiment of the present invention.

Referring to the drawings, the rod-shaped straight electrodes (hereinafter referred to as 'electrode rods') 100 have a structure in which they are spaced apart at regular intervals. The electrode 100 receives power from a power supply unit configured at upper and lower portions, that is, an upper power supply unit 102a and a lower power supply unit 102b. At this time, power distribution lines 104a and 104b are formed so that the power is uniformly supplied to each electrode 100. The power distribution lines 104a and 104b provide the same power supply line so that the power loss transmitted to each electrode 100 is supplied in the same phase without being generated differently according to the distance of the electrode 100 from the feed point. It must be formed.

The electrode rods 100 receiving power from the upper power supply unit 102a are alternately connected such that phases are supplied in an order of 0 ° and 180 °. In addition, the other electrode 100 located between the electrode rods 100 that receive power from the upper power supply unit 102a is supplied from the lower power supply unit 102b in an arbitrary phase in which the phase of the supply power is adjustable. That is, the electrode rods 100 that receive power from the upper power supply 102a and the lower power supply 102b are alternately arranged one by one to be separated from each other.

Between the power supply unit 102a, 102b and the power distribution line 104a, 104b, a first matching unit 103a and a second matching unit for adjusting impedance so that ultra-high frequency power is efficiently provided to the electrodes 100. The part 103b is provided.

As described above, each of the electrodes 100 serves as a feed point at which one end is supplied with power, and the other end is floating or grounded. In this case, if each of the electrodes 100 is grounded, since current is induced in the electrodes 100, a magnetic field around the electrode 100 is formed to form an inductively coupled plasma, thereby increasing the plasma density.

The electrode 100 is made of anodized aluminum, a material coated with an insulating material around a metal rod, such as silicon dioxide (SiO 2), quartz or other insulating materials such as Teflon, etc. in a tube (tube) structure. . The electrode 100 may also provide a role for supplying gas into the chamber in the plasma generator of the present embodiment. Accordingly, at least one gas discharge hole (not shown) is formed in the electrode 100 to supply the gas. The number of gas discharge holes is preferably provided to vary in number and diameter depending on the size of the substrate on which the plasma is formed.

Subsequently, as shown in FIG. 2, the electrodes having the same phase and the same power as the electrodes (ie, electrodes indicated by 'A' and 'B') that are supplied with two different phases from the electrode 100 are arranged. Two standing waves 130 and 140 are formed in the entire electrode structure by the supplied electrodes (electrodes denoted by 'C'). Specifically, in the state in which the electrodes of the 'A' phase, the 'B' phase, and the 'C' phase are arranged in FIG. 2, the electrodes of the 'A' phase and the 'C' phase are supplied with power in a state facing each other. The first standing wave 130 is formed by being connected to each other through the plasma. In addition, the second standing wave 140 is formed by the electrodes of the 'B' phase and the 'C' phase.

In addition, the electrodes having the 'C' phase from the lower power supply 102b are alternately supplied to the electrodes having the 'A' phase and the 'B' phase from the upper power supply 102a. When the power having an arbitrary phase is supplied to the three powers, the three powers may interfere with each other to uniformly generate plasma.

Meanwhile, in the above-described embodiment, the power supply unit for supplying power to the electrode 100 is configured at the top and the bottom, respectively, as shown in FIG. 3, only one power supply unit 110 is provided and the switching unit 120 is provided. The switching operation of the power supply allows the phases of 0 ° and 180 ° to be alternately supplied to the electrodes having the 'A' phase and the 'B' phase, and the same phase is supplied to the electrode having the 'C' phase. It can also be configured. When the power supply is performed, impedance matching by the matching units 103a and 103b occurs, and power supply to each electrode is uniformly provided by the power distribution lines 104a and 104b.

Next, a plasma generating apparatus and method according to the present invention having the configuration as described above will be described in detail with reference to a preferred embodiment shown in the accompanying drawings.

In FIG. 2, the electrodes 100 that receive power from the upper power supply unit 102a are alternately divided into two electric powers having different phases ('A' phase and 'B' phase) by the upper power supply unit 102a. Will be supplied. In addition, the electrode having an arbitrary phase from the lower power supply 102b is supplied to the electrode that is positioned between the electrodes having the 'A' phase and the 'B' phase, that is, the electrode connected to the lower power supply 102b. The power supply is uniformly performed by the first matching section 103a and the second matching section 103b, and the power distribution lines 104a and 104b corresponding thereto.

As such, when the electric power having a different phase is supplied to the electrode 100 from the upper power supply 102a and the same phase is supplied from the lower power supply 102b, ultra-high frequency is generated from the electrode 100 and the electrode ( 100) around the plasma is generated.

Accordingly, due to the plasma generation, the first standing wave 130 is formed by the two electrode rods of the 'A' phase and the 'C' phase, and the second standing wave is formed by the two electrode rods of the 'B' phase and the 'C' phase. 140 is formed. In this case, when the phase supplied to the electrode rod connected to the lower power supply unit 102b is adjusted, the positions of the first standing wave 130 and the second standing wave 140 are changed.

However, simply changing the position of the first standing wave 130 and the second standing wave 140 may not form the plasma uniformly. Accordingly, when the first standing wave 130 and the second standing wave 140 are formed in a state where different phase differences supplied to the electrode from the upper power supply 102a are separated by 180 ° (π), the first standing wave 130 and the second standing wave 140 are formed. The first standing wave 130 and the second standing wave 140 may have a phase difference of 90 ° (π / 2) and form a uniform plasma as a whole.

In other words, when the lower power supply unit 102b supplies power having an arbitrary phase, the lower power supply unit 102b has a phase of about 90 °, which is approximately halfway between the upper phases so that the plasma can be uniformly formed in the electrode 100. It should be.

The process in which the first standing wave 130 and the second standing wave 140 have a phase difference of 90 ° is described by the following relations.

l (1) = COS2 (2πZ / λ + (θ1-θ2) / 2) ---- Relationship (1)

l (2) = COS2 (2πZ / λ + (θ1 + π−θ2) / 2) = COS2 (2πZ / λ + (θ1-θ2) / 2 + π / 2)-(2).

I = I (1) + I (2) ----------- Relationship (3)

= COS2 (2πZ / λ + (θ1-θ2) / 2) + COS2 (2πZ / λ + (θ1-θ2) / 2 + π / 2)

= COS2 (2πZ / λ + (θ1-θ2) / 2) + SIN2 (2πZ / λ + (θ1-θ2) / 2)

= 1

Where I1: upper side intensity, I2: lower side intersity, z: position on the electrode, θ1: phase of the potential from the upper side, θ2: phase of the potential from the lower side

As such, two electric powers 180 degrees out of phase from the upper power supply 102a are sequentially supplied to the electrodes of the 'A' phase and the 'B' phase in the order of 0 ° and 180 ° and the lower power supply 102b is provided. When a power supplying an arbitrary phase that is adjustable from the 'C' phase electrode is supplied to the 'C' phase electrode, the phase of the first standing wave 130 and the second standing wave 140 has a phase difference of π / 2, and thus the powers By the interference of the to provide a condition that can generate a plasma uniformly.

That is, in this embodiment, the plasma cannot be generated uniformly only by applying a power 180 degrees out of phase from the upper power supply 102a, and only when the third power is applied from the lower power supply 102b. It satisfies the condition for generating uniformly.

In this way, even if the time changes, the phase between the plasma satisfies 90 degrees, thereby forming a uniform plasma, and thus the plasma can be uniformly processed at the front of the substrate.

Meanwhile, in the present embodiment, the power supply units of the upper power supply unit 102a and the lower power supply unit 102b are not separately configured, and power is supplied from one power supply unit 110 according to the switching operation of the switching unit 120. Can also be fed to the top and bottom of the). Of course, when power is supplied to the upper portion of the electrode 100, the phase difference of each neighboring electrode of the electrode receiving the upper power should be 180 °.

As described above, the present invention described in the above embodiment stabilizes a uniform plasma while compensating standing waves by supplying an arbitrary phase from the opposite side to the electrodes arranged between the electrodes receiving the phases in the structure receiving the two phases. Can be formed and maintained.

On the other hand, the plasma generating apparatus of the present invention is applied to perform a thin film formation process and a thin film etching process, which will be described with reference to FIGS. 4 and 5.

First, FIG. 4 is a flowchart of a thin film forming process using the plasma generator of the present invention. The thin film formation of FIG. 4 provides an example of forming a silicon thin film for a silicon solar cell.

In step 200, the glass or metal or plastic substrate is heated to a temperature of 100 to 250 degrees to form a silicon thin film, and in step 202, a mixed gas of SiH 4 / H 2 is introduced into the chamber through a gas discharge hole of the electrode 100. Supply.

In step 204, the mixed gas is supplied in the chamber to be supplied with power from the top of the electrode in the same direction, and the neighboring electrodes are alternately supplied (or at the same time) with two electric powers of 180 ° out of phase. do. In addition, in step 206, the other electrode positioned between the two electrodes 100 receiving the electric power is supplied with power of the same phase from the bottom. The power supply is uniformly supplied by the power distribution structure.

As such, when one electrode of the electrode and the electrode immediately neighboring are supplied with power in opposite directions, two standing waves are formed at a predetermined position of the electrode. In this case, if the phase applied from the lower part of the electrode is adjusted such that the standing wave has a phase difference of 90 ° as in step 208, the plasma can be uniformly generated in step 210. Such plasma forms a thin film on the substrate.

Next, FIG. 5 is a flowchart of a thin film etching process using the plasma generator of the present invention. The thin film etching process of FIG. 5 is an embodiment of an etching process of a silicon oxide film.

In this case, the pressure in the chamber is first adjusted in step 220, and then in step 222, CF4 gas and Ar gas are mixed and supplied into the chamber through the discharge hole of the electrode.

In operation 224, when the etching gas is supplied into the chamber, the neighboring electrodes are alternately supplied with two electric powers having different phases 180 ° from the top of the electrode. In addition, in step 226, the same phase electric power is supplied from the lower part of the electrode. The power supply is uniformly supplied by the power distribution structure.

As such, when one electrode of the electrode and the neighboring electrode are supplied with power in opposite directions, two standing waves are formed at a predetermined position of the electrode. In this case, as in step 228, the standing wave is adjusted from the bottom of the electrode to have a phase difference of 90 °, and in step 230, the thin film formed on the substrate is etched while generating plasma uniformly.

Although described with reference to the illustrated embodiment of the present invention as described above, this is merely exemplary, those skilled in the art to which the present invention pertains various modifications without departing from the spirit and scope of the present invention. It will be apparent that other embodiments may be modified and equivalent. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

For example, although the present invention has been described for the embodiment of forming a plasma with a predetermined thickness using ultra-high frequency, the present invention can be applied to the formation of a micro crystal silicon film of a solar cell, and particularly effectively in a large area or a high frequency. Can be formed. In addition, it can be applied to a system using a large-area plasma, such as dry etching using a high frequency power supply, a deposition equipment, a large-area etching equipment, a cleaning (cleaning) equipment, a surface treatment equipment using a plasma.

As described above, the plasma generating apparatus and method of the present invention have the following effects.

First, the present U-shaped electrode is provided so that the conditions for creating two plasmas having a phase difference of 90 ° where the standing waves generated along the traveling direction are satisfied are uniform. It can be applied to a wider process range. That is, in the case of a U-shaped electrode, the phase of power returned in the opposite direction should be adjusted to the length of the electrode. In this case, if the process conditions are changed, the system such as the electrode length should be changed, but the present invention can arbitrarily adjust the phase of the lower electrode. The same system can be applied to any electrode length or process conditions to form a uniform plasma.

In addition, since the phase difference of the standing waves is π / 2 to maintain a uniform plasma even when the time changes, it is possible to suppress the local temperature rise of the electrode, which can be generated by concentrating the plasma on one side, and uniformly plasma at the front of the substrate. There is also an effect that can be handled.

Claims (15)

A plurality of straight electrodes arranged at regular intervals, Any one electrode of the electrode and the neighboring electrode is provided with an upper power supply and a lower power supply at the top and bottom of the electrode to receive power in the opposite direction, The electrode that is powered by the upper power supply unit is configured such that the power supply is alternately supplied to each other alternately with 0 ° and 180 ° phases, and the electrode that is powered by the lower power supply is equally supplied in an arbitrary phase. Plasma generator, characterized in that. The method of claim 1, And a power distribution structure formed at the upper power supply unit and the lower power supply unit such that electric power is equally supplied to the electrode. The method according to claim 1 or 2, And a power supply unit for supplying power to the electrode, and configured to supply power to the upper and lower ends of the electrode by switching means. The method of claim 1, The electrode rod is characterized in that the anodized aluminum, stainless (SUS), the plasma generating device characterized in that the structure covered with a material coated with an insulating material around the metal rod in a tube state. The method of claim 4, wherein The insulating material is silicon dioxide (Si02), quartz, characterized in that the Teflon is used plasma generating apparatus. The method according to claim 1 or 4, Wherein the electrode is a plasma generating device, characterized in that the structure capable of introducing gas into the chamber in the plasma film forming and etching apparatus. The method according to claim 1 or 4, One end of the electrode is floating (floating) or grounded plasma generator characterized in that the configured. The method of claim 1, The high frequency power source is a plasma generator, characterized in that the ultra-high frequency of more than several hundred MHz from the radio frequency of 13.56MHz. Heating the substrate provided inside the chamber to a constant temperature, Supplying a mixed gas through the discharge hole of the electrode rod of claim 1 in the chamber; In the state where the mixed gas is supplied, two powers of different phases are sequentially applied from the upper part of the electrode by the upper power supply part, and the other electrode located between the electrodes to which the power is applied is lowered by the lower power supply part. Receiving power having the same phase in Adjusting the phase difference between two standing waves formed in the electrode structure in which the electrode rods are arranged by the power supply And forming a thin film on the substrate by a plasma uniformly formed in the electrode structure by controlling the phase difference. Supplying an etching gas into a chamber in which a thin film-formed substrate is installed, through a discharge hole formed in an electrode bar, Applying power having two phases out of phase at the top of the electrode, and the other electrode located between the electrodes to which the power is applied; Adjusting the phase difference between two standing waves formed in the electrode structure in which the electrodes are arranged due to the power supply; And etching the thin film formed on the substrate by a plasma uniformly formed in the electrode structure by controlling the phase difference. The method according to claim 9 or 10, Plasma generating method characterized in that the phase can be arbitrarily adjusted by the power supplied from the lower electrode. The method of claim 11, And the formation position of the standing wave is changed by the phase control. The method according to claim 9 or 10, The phase supplied to the upper portion of the electrode is a plasma generation method, characterized in that the phase of 0 ° and 180 ° are alternately supplied. The method of claim 13, And when the phases are separated and supplied at 180 °, the two standing waves have a phase difference of π / 2. The method according to claim 9 or 10, Plasma generation method characterized in that the plasma is uniformly formed by the mutual interference of the two power supplied to the top of the electrode and one power supplied to the bottom of the electrode.

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